| 1. |
- Din, Salah Ud, et al.
(author)
-
The Purification and Characterization of a Cutinase-like Enzyme with Activity on Polyethylene Terephthalate (PET) from a Newly Isolated Bacterium Stenotrophomonas maltophilia PRS8 at a Mesophilic Temperature
- 2023
-
In: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 13:6
-
Journal article (peer-reviewed)abstract
- A polyethylene terephthalate (PET)-degrading bacterium identified as Stenotrophomonas maltophilia PRS8 was isolated from the soil of a landfill. The degradation of the PET bottle flakes and the PET prepared as a powder were assessed using live cells, an extracellular medium, or a purified cutinase-like enzyme. These treated polymers were analyzed using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The depolymerization products, identified using HPLC and LC-MS, were terephthalic acid (TPA), mono(2-hydroxyethyl)-TPA (MHET), and bis(2-hydroxyethyl)-TPA (BHET). Several physicochemical factors were optimized for a better cutinase-like enzyme production by using unique single-factor and multi-factor statistical models (the Plackett–Burman design and the central composite design software). The enzyme was purified for homogeneity through column chromatography using Sephadex G-100 resin. The molecular weight of the enzyme was approximately 58 kDa. The specific activity on para nitrophenyl butyrate was estimated at 450.58 U/mg, with a purification of 6.39 times and a yield of 48.64%. The enzyme was stable at various temperatures (30–40 °C) and pH levels (8.0–10.0). The enzyme activity was significantly improved by the surfactants (Triton X-100 and Tween-40), organic solvent (formaldehyde), and metals (NiCl2 and Na2SO4). The extracellular medium containing the cutinase-type enzyme showed a depolymerization yield of the PET powder comparable to that of Idonella skaiensis IsPETase and significantly higher than that of Humicola insolens thermostable HiCut (HiC) cutinase. This study suggests that S. maltophilia PRS8 is able to degrade PET at a mesophilic temperature and could be further explored for the sustainable management of plastic waste.
|
|
| 2. |
- Hazer, Baki, et al.
(author)
-
Free Radical Polymerization of Dimethyl Amino Ethyl Methacrylate Initiated by Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) Macroazo Initiator : Thermal and Physicochemical Characterization
- 2023
-
In: Journal of Polymers and the Environment. - 1566-2543. ; 31:8, s. 3688-3699
-
Journal article (peer-reviewed)abstract
- A novel macro intermediate based on poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) was synthesized for use in the copolymerization with dimethyl amino ethyl methacrylate (DMAEMA). Methyl amino ethanol was reacted with PHBHHx to prepare a dihydroxy terminated polyester. The hydroxyl ends of the obtained PHBHHx derivatives were capped with 4,4’-azobis cyanopentanoic acid to obtain the PHBHHx macroazo initiator (PHBHHx-AI) for free radical copolymerization of DMAEMA at 70oC. A steady increase in DMAEMA units in the synthesized block copolymer as a function of time was observed. The overall rate constants for the free radical polymerization of DMAEMA initiated by PHBHHx-AI was k = 2.33 × 10− 4 Lmol-1s-1. Block copolymers were characterized using the 1 H NMR, FTIR, DSC and TGA techniques.
|
|
| 3. |
- Mankar, Smita V., et al.
(author)
-
Short-Loop Chemical Recycling via Telechelic Polymers for Biobased Polyesters with Spiroacetal Units
- 2023
-
In: ACS Sustainable Chemistry & Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 11:13, s. 5135-5146
-
Journal article (peer-reviewed)abstract
- Spirocyclic acetal structures have recently received growing attention in polymer science due to their dual potential to raise the glass transition temperature (Tg) and enable chemical recycling of biobased polymers. In the present work, a vanillin-based diol with a spirocyclic acetal structure was incorporated in a series of rigid amorphous polyesters based on neopentyl glycol and dimethyl terephthalate (DMT). Up to 50 mol % of spirocyclic diol (with respect to DMT) could be incorporated in the copolyesters, but a reasonably high molecular weight was only achieved when ≤30 mol % of the spirocyclic diol was used. The presence of the spiroacetal units in the polyesters not only enhanced the Tg (up to 103 °C) and thermal stability (T5 ≥ 300 °C) but also the oxygen barrier of solution-cast films. We found that the acetal units in the copolyesters could be selectively hydrolyzed under acidic conditions while virtually retaining all of the ester bonds in the polymer backbone. After acidic hydrolysis, telechelic polymers exclusively terminated by two aldehyde end groups were obtained. In this work, we have demonstrated that these telechelic polyesters can be conveniently converted back into poly(acetal-ester)s via cycloacetalization reactions with pentaerythritol.
|
|
| 4. |
|
|
| 5. |
- Wagner-Egea, Paula, et al.
(author)
-
Marine PET Hydrolase (PET2) : Assessment of Terephthalate- and Indole-Based Polyester Depolymerization
- 2023
-
In: Catalysts. - 2073-4344. ; 13:9
-
Journal article (peer-reviewed)abstract
- Enzymatic polyethylene terephthalate (PET) recycling processes are gaining interest for their low environmental impact, use of mild conditions, and specificity. Furthermore, PET hydrolase enzymes are continuously being discovered and engineered. In this work, we studied a PET hydrolase (PET2), initially characterized as an alkaline thermostable lipase. PET2 was produced in a fusion form with a 6-histidine tag in the N-terminal. The PET2 activity on aromatic terephthalate and new indole-based polyesters was evaluated using polymers in powder form. Compared with IsPETase, an enzyme derived from Ideonella sakaiensis, PET2 showed a lower PET depolymerization yield. However, interestingly, PET2 produced significantly higher polybutylene terephthalate (PBT) and polyhexylene terephthalate (PHT) depolymerization yields. A clear preference was found for aromatic indole-derived polyesters over non-aromatic ones. No activity was detected on Akestra™, an amorphous copolyester with spiroacetal structures. Docking studies suggest that a narrower and more hydrophobic active site reduces its activity on PET but favors its interaction with PBT and PHT. Understanding the enzyme preferences of polymers will contribute to their effective use to depolymerize different types of polyesters.
|
|
